It has been recognized that there is a demand for various forms of information to be communicated to and from customer premises such as residences. This information includes, in particular, video-on-demand (VOD) and near-VOD (e.g. movies with stepped starting times) television programs in the downstream direction to the customer premises, upstream control information for selection of such programs, and bidirectional communications services.
Existing analog coaxial cable television distribution arrangements have not met this demand in view of their limited bandwidth and hence limited television channel capacity and inability, or limited ability, to carry communications upstream to the so-called head end. Future coaxial cable systems will enhance this capability by adding digital television and bidirectional communications services.
Optical fiber networks have the capability of meeting this demand, but do not generally extend to residential customer premises. Telephone subscriber lines (unloaded twisted pair cables) have until recently had insufficient bandwidth to carry video signals.
ADSL technology, for example using multicarrier modulation, makes it possible to send data at bit rates in excess of 6 Mb/s downstream, and simultaneously to communicate other data at lower bit rates as well as telephone signals bidirectionally, over a single telephone subscriber line, referred to as an ADSL loop. The principles of multicarrier modulation are described for example in "Multicarrier Modulation For Data Transmission: An Idea Whose Time Has Come" by John A. C. Bingham, IEEE Communications Magazine, Vol. 28, No. 5, pages 5-14, May 1990. An overview of ADSL is provided in an article by S. Fleming et al. entitled "ADSL: The on-ramp to the information highway", Telephony, Jul. 12, 1993, pages 20-26. This article describes an ADSL system in which four asymmetric 1.5 Mb/s channels are provided for transmission in a downstream direction from a telephone CO (central office) to a subscriber, in addition to various data channels and POTS (plain old telephone service) carried symmetrically (i.e. bidirectionally), via a two-wire telephone subscriber line. The four 1.5 Mb/s channels can together carry one, two, or four digital video signals with different levels of compression.
Thus three technologies, namely fiber/coax, fiber-in-the-loop or FITL, and ADSL systems, are being developed for delivering enhanced (e.g. digital) television services and bidirectional communications services to customer premises. These will converge in the customer premises, where it is highly desirable that they all use the same customer premises equipment and wiring.
Furthermore, the customer premises wiring or signal distribution arrangement must take into account a number of considerations, such as the different services required by different customers, different types of customer premises (e.g. single and multiple residential units), the desirability of avoiding bulky cables and rewiring in the customer premises, and ease of evolution as new services and facilities are developed and installed.
An object of this invention, therefore, is to provide an advantageous arrangement for distributing signals to customer premises.